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Courier Mail Server

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Courier Mail ServerSource code distributed under the GNU General Public LicenseFree

As courier-mta.org lists them, read 5 Oct 2026. The maker's own page has the final word.

Facts from Courier Mail Server's own pages

Authentication
Authentication options include PAM, LDAP, MySQL, and PostgreSQL, with PostgreSQL identified as beta on the features page. · courier-mta.org, 5 Oct 2026
Calendaring
Its webmail module includes basic web-based calendaring and scheduling, including a personal event calendar. · courier-mta.org, 5 Oct 2026
Compatibility
Courier can be installed on systems previously running sendmail or Qmail, but the site says it is not a fully compatible replacement for either. · courier-mta.org, 5 Oct 2026
Deployment
It can act as an intermediate mail relay, receive mail for multiple domains, or do both. · courier-mta.org, 5 Oct 2026
Distribution
The download page offers the complete server source tarball and separate packages for components including IMAP, SqWebMail, and maildrop. · courier-mta.org, 5 Oct 2026
Download
The download page lists Courier 2.0.7, dated 02-Aug-2026, as a source code tarball containing the mail server, IMAP server, webmail server, and maildrop filter. · courier-mta.org, 4 Oct 2026
Filtering
Integrated mail filtering supports administrator-installed external filters and recipient-specified rules through maildrop. · courier-mta.org, 5 Oct 2026
Integrations
The server can use LDAP, MySQL, or PostgreSQL-based authentication databases and supports LDAP-based mail routing. · courier-mta.org, 5 Oct 2026
Limitations
Courier does not implement ETRN and is not a fully compatible replacement for sendmail or Qmail; its integrated mailbox servers do not support mbox. · courier-mta.org, 4 Oct 2026
Limits
Courier does not implement ETRN, and its integrated mailbox access components do not support mbox mailboxes. · courier-mta.org, 5 Oct 2026
Mailing lists
Courier includes a mailing list manager with automatic bounce processing. · courier-mta.org, 4 Oct 2026
Mail services
Courier is an integrated mail and groupware server providing ESMTP, IMAP, POP3, webmail, and mailing list services. · courier-mta.org, 5 Oct 2026
Mail storage
Maildir is its native mail storage format, and integrated IMAP, POP3, and webmail components support maildir-based mailboxes only. · courier-mta.org, 5 Oct 2026
Platforms
The source should compile on most Linux and BSD-based POSIX operating systems, and may compile on Solaris and AIX with additional tools. · courier-mta.org, 5 Oct 2026
Product
Courier is an integrated mail and groupware server providing ESMTP, IMAP, POP3, webmail, and mailing list services. · courier-mta.org, 4 Oct 2026
Relay protection
The site says Courier is a closed mail relay by default and cannot accidentally be configured as a completely open relay. · courier-mta.org, 5 Oct 2026
Security
Courier supports STARTTLS and SSL for ESMTP, IMAP, POP3, and webmail; its ESMTP client can require a certificate signed by a trusted root CA. · courier-mta.org, 5 Oct 2026
Standalone components
The IMAP server, SqWebMail webmail CGI, and maildrop filter are also offered as separate packages usable with other mail servers. · courier-mta.org, 4 Oct 2026
Storage
Maildir is its native storage format; the integrated POP3, IMAP, and webmail servers work with maildir mailboxes only. · courier-mta.org, 4 Oct 2026
Support
The site lists an unmoderated courier-users mailing list for questions, bug reports, and comments, plus a separate read-only announcement list. · courier-mta.org, 4 Oct 2026
Transport security
The site lists STARTTLS and SSL support for ESMTP, IMAP, POP3, and webmail, and says the ESMTP client can require trusted-root-signed X.509 certificates. · courier-mta.org, 4 Oct 2026
Web administration
Most configuration can be adjusted through a web-based administration module. · courier-mta.org, 5 Oct 2026

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